# 回歸給出股票收益

$$R_ {股票} = 3,28 \％+ 1,65 * R_ {市場}$$

1. 最近一年股票的預期收益是多少？
2. 如果我們要計算折現率以評估現金流量，那麼預期收益會變化嗎？如果是，怎麼辦？

The basic CAPM - which is what your regression estimates - says $$R_S = R_f + \beta_S (R_{Market}-R_f)$$ where $$\beta_S = \frac{Cov(R_M,R_S)}{Var(R_M)}$$ i.e. the return of a certain stock depends only on the correlation with the market portfolio.

For your pricing equation to work, you will need to have an idea about the expected market (excess) return. In practice, often the historical mean return of an index (such as S&P 500, ...) is used, but that is very far from perfect. Only that assuming seems like an even worse idea to me...

Keep in mind that, if you want to estimate the regression, you need to use excess returns for the market, otherwise your intercept will be the wrong one (though beta should be fine).